PORTLAND – Two men who were the target of a drug investigation beat up an undercover drug agent and threatened to kill him, officials said Friday.

Harold J. Ferrar, 27, and Ryan Hunt, 24, both of Portland, were arrested as they tried to flee Thursday afternoon, the Maine Drug Enforcement Agency said. Both face charges of assault, armed robbery and aggravated trafficking of heroin.

Special Agent Erik Larsen, who was on loan from the South Portland Police Department, was negotiating a drug purchase when Ferrar pressed the barrel of a handgun to Larsen’s neck and threatened to kill him if he didn’t turn over his money, the DEA said.

Larsen handed over his wallet and then the men proceeded to beat him, officials said. He was treated at Maine Medical Center in Portland and then released.

The undercover operation in the Kennedy Park neighborhood was part of a two-month investigation in and around Portland Housing Authority properties.

Seized during the arrest were a .22-caliber handgun, a bag of heroin and $1,400 in drug proceeds, along with Larsen’s money. Ferrar and Hunt were being held on $100,000 bond at the Cumberland County Jail.